CASA Contributed Script: Align Cubes by Velocity

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Align Two Cubes According to their Velocity Axes

Hopefully this will soon be deprecated by core CASA functionality. In the meantime please direct bug notes, suggestions, or just note use to aleroy at nrao dot edu.

This is also planned future functionality for CASA but in the interim users working with multiple transitions or multiple observations of the same transition may find it desirable to align one cube so that its velocity axis matches that of another. This allows one to readily overlay the two cubes in the CASA viewer (which aligns data cubes by their spectral pixel rather than their velocity value).

Download these scripts and follow the "buildmytasks" procedure described in the CASA Cookbook | here. You can also access the functionality in python directly by importing task_alignbyvel.py.

Once you have the task, simply pick a "template" cube that holds the desired velocity axis, an "infile" that holds the cube to be aligned, and specify an "outfile" to hold the output CASA image file. For example you could align the CN and CO images from the ALMA SV data on NGC 3256 like so:

# In CASA
CN_im = 'n3256_CNlo.im/'
CO_im = 'n3256_CO.im/'
out = 'n3256_CNlo_to_CO.im/'
alignbyvel(infile=CN_im,
           outfile=out,
           template=CO_im,
           overwrite=True)